Electric motor



G. B. COLEMAN.

ELECTRIC MOTOR.

Patented Dec. 12,1922.

APPLICATION FILED .IAN- 3,1921.

' y rram/Eys Patented Dec. l2, 1922.

UNITED STATES t i A 1,438,361

PATENT OFFICE.

GEORGE B. COLEMAN, OF SAN FRANCISCO, CALIFORNIA, ASSIGNOR TO MAJIK ELEC- TRIC APPLIANCE COMPANY, OF SAN FRANCISCO, CALIFORNIA, A CORPORATION OF CALIFORNIA.

ELECTRIC MOTOR.

Application filed January 3, 1921. Serial No. 434,518.

To all whom t may concern Be it known that I, GEORGE B. COLEMAN,

a citizen of the United States, and' resident of the city and county of San Francisco, State of California, have invented new and useful Improvements in Electric Motors, of

which the following is a specification.

My invention has for its principal object the arrangement of parts and construction whereby I attain a complete assembled motor of miniature size suitable for holding in the hand, and is particularly adapted t0 dental work or the operation of small household devices and clippers and brushes and the like. By my construction a preferred form of which is set forth below, it will be seen that the cost of manufacture and particularly the windings of the several magnets, is much cheaper than in other types; also that the arrangement of the rotor and stator is such that amaxium leverage about the axis of rotation or a maximum torque is obtainable within limits of size.

Another object of my invention is an adjustment whereby any required variation of speed may be readily produced by varying the air gap between lthe stator and the rotor. This I prefer to accomplish by a positive adjustnient in an axial direction oi' the rotor. VWith the arrangement of the coils which I employ a greater number of turns may be employed. on the several coils than in other types of miniature motors, and I employ high resistance windings so that the motor is readily applicable to operation on commercial lighting circuits, utilizing but comparatively few milliamperes. In ths way the coils are protected from burnouts which would otherwise occur with 40 low resistance windings.

These objects I attain for example by the preferred construction set forth in the drawing and description below, which construction consists of a lurality of magnets assembled about the axis of the rotor shaft and which form a stator, and a second plurality of similar magnets mounted on said shaft. All of these magnets consist of cores Cil:

over .which spools containing the necessary windings may be readily slipped. The rotor is provided with a suitable commutator and the main casing or shell supports .a air of brushes engaging said commutator. he stat-or and rotor are of the same diameters and the windings and magnetic cores are disposed parallel with and symmetrically about the axis. tends through one end of the casing and is provided with a suitable end fitting preferably insulated so that any device which it is desired to operate may be slipped thereon and engaged to drive from the said shaft. The opposite end of the shaft is carried in a positive bearing held against-axial movement rand the said bearin is carried in a suitablesleeve and made a justable and the entire bearing, and therefore the rotor shaft carried in it, is made axially adjustable by a set screw engaging one side of the bearing and a compressed spring engaging the opposite side and holding the bearing against the said set screw. The set screw I extend beyond the exterior of the casing so that during operation of the motor the air gap may bc varied between the stator and the rotor and consequently varying the revolutions at which the rotor will operate under given conditions of electric service supply and load. u

lly referring to the accompanying drawings my invention will be made clear.

Figure l is a longitudinal view of the interior construction of my motor with the outer casing or shell show; section, and taken on the right angled line I-I of Fig. 2.

Figure 2 is a cross section of Fig. 1 on the line II-II.

Fig. 3 is an enlarged sectional detail of the shaft bearing showing the adjustable features thereof.

Fig. et is a diagrammatic showing of the windings and circuit connections, commutator and brushes.

Throughout the figures similar' numerals refer to identical parts.

The motor is adapted to be housed within The rotor shaft exy a casing indicated by the numeral 1 having a rear end 2 and a cover member 3 and prei'erably an insulated lining 35. The

cover is provided with a bearing i adapted to carry the rotor shaft 5. This shaft 5 may be tapered or provided with any suitable 'fastening means as at 6 and adapted to carry an extension member or motor operated connection 7 which l have shown in the drawings as having a brush 8 suitable for brusi f the rotor coils are arranged the iluralitY o1l stator coils as 16,17, 18 and 19, and the coils or the stator and rotor are arranged in` electrical series through the brush and commutator contacts so that current will tiow in the rotor, and be periodically reversed through the commutator such that the rotor coils will be attracted by one group et stator magnets and repelled by the other intermediate set of stator magnets. ln this way motion will be imparted to the rotor and thence to the shaft 5, it being understood et course that the several magnets 12, 13, 111, 15', 16, 17, 18 and 19 are suitably mounted upon basesy ot magnetic material 2O and 21 respectively, The base 20 .l pre- '1er to form ot disc shape having a hub 22 mounted upon the said shaft and the base 21 l prefer to iorm ot a shape suited to fit i snugly within the casing 1. vVhen this base 21 is fitted in place within casing 1, l roll a bead or groove 36 in the said casing 1, thus crimping the base 2l permanently in place in vthe casino l and aii'ainst the and alato 2.

'llhis secures alignment oll the axis oi symmetry o: the magnets 1G, 1T, 1S and 19 with the axis ot the sliaiit' .ln the center oil the base 21 l'A lit the l'icariiig stai'ida` rd 23 carrying i; hearing about the shaft and having mially disposed coil spring 25 within the standard. rlhis spring is normally under compression tending to Jorce the hearing shell 26 against the end 27 ot the set screw 28, which set screw passes through the block 21 and cover 22 and by its rotation varies the position or the bearing shell 26 within the sleeve 23. rfhe bearing shell 26 may be provided with a bearing of smaller diameter than the shaft i and engage a groove therein, or may preferably i'orni a part of a ball bearing 29, which latter' engages with the shalt as shown in Fig. 3. By this construction it will be seen that the rotation oi" the screw 28 will advance the bearing 2G and sliaiit 5 to increase the air gap between the stator and the rotor or by a rotation ot the set screw 28 in the opposite direction, the coil spring 25 will torce the shatt 5 and therelfore the rotor in the direction towards the stator and reduce the air gap therebetween and consequently increase the speed. Ait SO l have shown an oil hole through the screw 28 tor introducing lubricant as may be required within the pocket $31 and shaft step bearing 26. rt 32 are electrical connections from a suitable sourceo'f electric energy not shown. The cover plate 3 is adapted te slide within tlieycasing 1 and to either be compressed therein or engage by suitable holding` .means in any well known way.

lt is to be understood that the` driven member i is interchangeable on the end 6 ot the shaft 5 with other devices having similar sockets whereby devices requiring power, as polishing wheels, etc.,1`nay be readily iitted thereon at the joint 6. At 38 is shown a switch oi' any well known type tor starting or stopping the motor. I prefer toprovide the extension o1' the shai't 5 with an insulating union as at 34 whereby the body oli the motor and ot its parts are thoroughly insulated from the terminal device, especially where the motor is intended to be used for dental worlr.k

The operation is as Yfollows:

lerminals 32 areconnected to any suitable source of electrical energy as the well known socket Jor incandescent lamps, switch 33 is closed and coils 12, 13, 1li and 15 oic the rotor coils 16, 17, 18 and 19 are all energized. rThe coils of the rotor as shown in llig. i have just passed through a cycle ot attraction and in the next instant" will be polarized the same as the adjacent coils of the stator and will therefore be repelled until coil 12 comes very close to coil 18 and during which `time coil 12 has been attracted by coillS. ifi. similar cycle ot attractions and repiilsions taires place between the other coils ol the stator andiiiitor thus causing a rotation oil" the shaft.

rlhe intensity t the magnetic held determines the speed at which the motor will operate tor anyA given load and this field intensity may be varied by the Set screw 28,

increasing or decreasing the air gap between the stator and the rotor, and consequently varying the speed of the motor independent `ot any variation or' the voltage or other eX- ln a dynamo electric machine, a shaft,

a stator having cores extending parallel to the shatt7 a rotorfmounted on the shaft cooperating With the stator and having cores separated by an air gap from the cores of the sta-tor, and means for adjusting this gap comprising a stationary guide, a bearing for the shaft slidably mounted in the guide, said bearing and shaft being so arranged that` there can be no relative axial movement between them, a spring urging said bearing 10 in one direction and a thumb nut urging the hearing in the other direction.

GEORGE B. COLEMAN. 

